SOC Estimation During Plug-In Charge Using Voltage Interruption
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for estimating the state-of-charge (SOC) of rechargeable energy storage systems during plug-in charge mode are inaccurate due to lack of excitation, leading to potential overcharge or undercharge, especially when adaptive regression methods fail to provide stable SOC values.
Innovation Solution
A system and method that involve measuring voltage and current during charging, pausing the charge to calculate static resistance, computing open circuit voltage, and determining SOC using these values, allowing for precise SOC estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage-based SOC calculations using recursive least square algorithm are employed, then SOC estimation is possible, but the method requires sufficient excitation in voltage and current signals which is not available during constant current charging
Solution Approach 1:
The patent changes the measurement parameters by measuring open circuit voltage at multiple different states of charge during the charging process. By taking voltage measurements at different charge levels and using the relationship between open circuit voltage and SOC, the system can establish an accurate SOC estimation without requiring signal excitation that would disrupt the charging process.
2Ease of manufacture
If coulomb counting technique is used for SOC estimation, then the method is simple to implement, but it depends on known starting points for open circuit voltage and initial SOC which cannot be predicted with absolute certainty
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the relationship between measured current, time, and open circuit voltage during charging. By using the measured open circuit voltage at different charge levels as feedback to verify and correct the SOC estimation, the system eliminates the need to assume accurate starting points while maintaining implementation simplicity.
Solution Approach 2:
The patent performs preliminary measurements of open circuit voltage at the beginning of the charging process and at intermediate points. These preliminary voltage measurements establish a baseline relationship between voltage and charge level, allowing the system to accurately determine SOC without relying on uncertain initial SOC values from previous driving cycles.
3Productivity
If charge continues without interruption to maintain productivity, then charging efficiency is high, but accurate SOC measurement becomes difficult due to lack of open circuit voltage conditions
Solution Approach 1:
The patent employs periodic brief interruptions in the charging process at strategically selected points. During these short interruptions, the system measures the open circuit voltage to update SOC estimation. The interruptions are brief and scheduled to minimize impact on overall charging efficiency while providing sufficient data points for accurate SOC determination throughout the charging process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides accurate and stable SOC estimation, preventing overcharge or undercharge, increasing RESS life, improving fuel economy, and reducing emissions.
Implementation Method 1
calculating a resistance based on the first measured voltage, the second measured voltage and the measured current, calculating an open circuit voltage of the RESS based on the resistance, the second measured voltage, the measured current
Data Source
AI summary
A system and method for estimating parameters of a rechargeable energy storage system during a plug-in charge mode include reading a first measured voltage and a measured current from the rechargeable energy storage system while charging the rechargeable energy storage system during a plug-in charge mode, interrupting the charge to stop current flow to the rechargeable energy storage system for a predetermined period of time, reading a second measured voltage during the charge interrupt, calculating a resistance based on the first measured voltage, the second measured voltage and the measured current, calculating an open circuit voltage of the rechargeable energy storage system based on the resistance, the second measured voltage, the measured current and determining the state-of-charge for the rechargeable energy storage system using the open circuit voltage.